Color photography



June 25, 1935.

FIG-/ Filed Nov. 30, 1931 2 Sheets-Sheet 1 BLACK OBJECT WHITE FIG-2 u 2Q 3 a:

m w i! BLUE GREEN YELLOW RED 0 L 0 L 0 L 0 L CLEAR CLEAR WHITE CLEARBLAGK 4 CLEAR RED YELLOW RED D L D L D C I CLEAR BLUE BLUE OLE/4R CLEARBLACK COLORS OF FIN/SHED NEGA TIVEBY TRANSM/TZ'ED LIGHT BLUE L W REDBLUE GREEN VELLO L D L D L D L D INVENTOR.

A TTORNE YS.

NEG/1 TIVE June 25, 1935. L. M. DIETERICH 2,005,970

COLOR PHOTOGRAPHY Filed Nov. 30, 1951 2 Sheets-Sheet 2 WHITE BLA CK BLUEGREEN YELLOW RED L D L D L D L D BLACK CLEAR GRAY GRAY CLEAR CLEAR BLUECLEAR BLUE BLUE CLEAR CL54R v YELLOW kELLow 0 L 0 L BLACK WHITE BLUEGREEN YELLOW RED 0 y L 0 L 0 L 0 L k a o: (L

COLORS 0F F/N/SHED PR/NT B) T/MNSM/TTED LIGHT INVENTOR. Luz/W47 Mfl/efer/cfi A TTORNE YS.

Patented June 25, 1935 PATENT OFFICE COLOR PHOTOGRAPHY Ludwig M.Dieterich, Los Angeles, Calif., assignor to Detracolor Ltd., acorporation of Nevada Application November 30, 1931, Serial No. 578,059

(01.95-2) This invention relates to color photography in accuratepredetermination of these values (subgeneral; and more particularly tothe production of photographic plates or films and emulsions;

and to a process whereby the desired color effects 5 are produced.

it possible to produce more accurate and heretofore unobtainable colorefiects, and at the same time more economically than present color 1photography methods.

Another object oi-this invention is to provide, mr color photography,identical or similar emulsions in single or double coated stock for bothnegatives and positives, thereby greatly increasing the simplicity ofprocessing and decreasing the cost of the raw stock and its processing.

Still another object of this invention is to obviate the necessity ofany changes,special designs, attachments or accessories relating tostandard cameras, magazines or projection machines, such as now used forblack and white photography, for adapting them to color work.

Another object of this invention is to secure a coloring agents.

Another object of this invention is to eliminate all possibilities ofhuman errors or faulty judgment in the selection and application ofcolors or tones during the processing of the respective light sensitiveemulsions. Another object of this invention is to impregnate one or morelight sensitive emulsions during their manufacture. with dyes orcoloring agents not of the complementary but of the same 1 color valuesto which they are sensitized.

Another object of this invention is to eliminate all special mechanicalor physical apparatus or methods to secure perfect registration of theimages of the respective emulsions both for the negatives and theirprints.

Another object of this invention is to provide a photographic colorprocess which is equally advantageously applicable to portraitphotography, lantern slides, and all types of transparencies; as

the need for the exercise or individual judgment on the part of themanipulator of the stock after exposure, for determining the properrelative color values; and instead,-to substitute tor-such exercise ofjudgment, a definite and substantially the prior art. One of the objectsof this invention is to make rigorous four color separation employingbut two ject only to the exposure values) during the manufacture. Thusthe color determinations are under exact control, which is not possibleby practicing 5 It is still another object of this invention to obviatethe necessity for any special lighting or other exposure conditions overthose normally used 'in black and white photography, but which are nownecessary when using substantially any 0 of the present commercial colorprocesses,

Another object 01 this invention is to reduce the danger of halationwhich now exists in prior methods, that utilize a series of single layeremulsions.

Another object of the invention is to provide a multiple layer emulsionof the sensitive medium for color work, in which the emulsions haveoverlapping ranges of sensitivity along the spectrum, but at the sametime, the combined emulsion is sensitive to the whole range of colors inthe spectrum.

The films used under this invention are preferably oi the singlecoating, multiple emulsions type for either the negative or thepositive. 25

The processing consists of a novel combination of steps well known intheir physical and chemical aspects and results.

In order to describe accurately how this invention may be practiced, abrief review of the ordinary photographic process is helpiul. Inphotography the light sensitive medium is usually an emulsion of asilver halide. This emulsion is usually supported on a baseor stock.Upon exposure the sensitive medium is affected approximately inproportion to the light intensity and to the length or exposure. Theemulsion can then be developed to cause that portion of the silver saltwhich had been affected during exposure to be reduced to metallicsilver. The unaffected or unexposed silver salts are not reduced tometallic 'silver but may be entirely removed by the process stood thatfurther description is unnecessary. It

' applies as well to the making of positives as to the making ofnegatives.

In color photography the problem is to change the black and white valuesobtained by the exwhen superimposed, produce the desired color effects.This is usually accomplished by first partially or completely bleachingthe emulsions, and then dyeing the emulsions with an appropriate colorso as to produce a colored transparency for each emulsion. when theseemulsions are superimposed, then the resultant transparencies representeither a positive or a negative in color of the object photographed. Ingeneral this invention employs the idea of providing two or moresuperimposed emulsions or layers which can be treated independently ofeach other to secure the desired color effects.

One of the characteristics of this invention is the pre-dyeing of one ofthe emulsions a color corresponding to the sensitivity range of thatemulsion and the coloring, either by dyeing or toning, of the otheremulsion with the color of the photographed object to which it issensitized, in contradistinction to the usual practice of usingcomplementary colors.

My invention possesses many other advantages, and has other objectswhich may be made more easily apparent from a consideration of oneembodiment of my invention. For this purpose I have shown a form in thedrawings accompanying and forming part of the present specification. Ishall now proceed to describe this form in detail, which illustrates thegeneral principles of my invention; but it is to be understood that thisdetailed description is not to be taken in a limiting sense, since thescope of my invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a cross section, greatly enlarged, of a sensitized negativeor positive plate or film utilizing the invention;

Fig. 2 is a diagram showing approximately the light sensitivities of thetop and bottom emulsions respectively;

Fig. 3 shows schematically the colored object to be photographed in thefirst band; and in successive bands the top and bottom emulsion colorcharacteristics of the negative during processing periods; and in thelowest band, the color characteristics of the finished negative; and

Fig. 4 shows schematically the color characteristics of the finishednegative in the first band and in successive bands, the top and bottomemulsion color characteristics of the positive during processingperiods; and in the lowest band, the color characteristics of thefinished positive.

This method and the related drawings, however, are to be considered inan illustrating but not limiting sense.

The negative film consists of a standard transparent base a on which iscoated a light sensitive silver emulsion c which in manufacture is dyedor impregnated with a soluble red dye. This red is of any well knowntype, in which low densities transmit yellow, and high densities red.The lower graph of the spectrogram shown in Fig. 2 of such an' emulsionshows highest transmission at 6500 (Angstrom units). It cuts off towardsthe infra red at about 7200; includes yellow (5850) and green (5350),cutting off at about4850, at the start of the blue transmission. Theordinates of this diagram are drawn to logarithmic values, so that thesensitivity of green and yellow is proportionately much less than isindicated in the diagram.

Ontop of this emulsion or on the other side of the base, anorthochromatic emulsion b is 7 y coated, the spectrogram of which isshown in the upper graph of Fig. 2. This shows start .of

transmission at 3800 with a maximum for blue (about 4850) and a secondbut lesser, peak in the green region.

Under this invention the following use is made of these spectrumcharacteristics as diagrammatically shown in Figs. 3 and 4.

For illustration an object to be photographed is shown as a horizontalband of squares in Fig. 3, showing from left to right successively nocolor (black), all colors (white), blue, green, yellow and red. Thisobject so labelled in Fig. 3 is merely a diagram. The respective areasmay be very much interspersed and in fact overlapping, but I showseparate oblong areas. The colored oblongs of blue, green, yellow, andred are split in half. The left hand half of each of these coloredoblongs is marked with a letter D to indicate that it is a dark shade;similarly the right hand half is marked with an L to indicate that thishalf of each oblong has a light shade.

The raw stock or film above described is used to photograph this object.After exposure the photographic plate or film is developed, washed,fixed, washed in water and other solutions and dried, the details ofwhich operations are hereinafter described.

Thereafter the top emulsion may be dyed blue under any well knownprocess, such as the one hereinafter explained in detail.

The red yellow dye of 'the bottom emulsion has two functions. It acts asa filter dye in order to produce the desired spectrum characteristicsfor the bottom emulsion and also produces in the finished negative orpositivemthe desired color values.

This can be achieved by one dye or by two dyes each producing the abovestated efiects. In such a case these two dyes may be soluble in twodiflferent solvents. As an example, the filter dye may be soluble inwater and the dye producing the final coloring in alcohol.

The possible errors due to the human element are eliminated and theprocessing greatly simplified by omitting the separate coloring of theemulsions during processing. Color bleeding between the two emulsions isunder this method also obviated.

An important characteristic of this form of my invention is the factthat a single processing sequence only is used for both emulsions inboth negatives and positives.

An example of a preferred detail application of this invention isherewith described as applied to motion pictures. 4

Under this invention, and this preferred example, the bottom layer c(corresponding in sensitivity to "panchromatic film), consists of asilver emulsion which is impregnated with a spirit soluble dye of thatclass which is a yellow color in light densities and red color for heavydensities, there being a gradual or continuous change from one color tothe other in accordance with the variations in density, a suitable dyefor this purpose is oleate of diethyl m-aminophenol succinein.

This dye acts as a filter and coloring agent for the silver halides andis chosen or such a concentration as to impart to this emulsion a lightsensitivity as shown in the lower spectro-' gram of Fig. 2.

This action may also be achieved by using a filter and an intermixedcoloring dye as previously stated.

On top of this emulsion'jayer the. layer of orthochromatic emulsion 5(corresponding in sensitivity to orthochromatic film), is placed, havingthe sensitivity characteristics as heretoforeexplained.

In processing the following operations may be employed:

1. After exposure the film is developed, as customary for black andwhile practice, in such as the customary borax developer. This reducesthe exposed silver halides of the emulsion to metallic silver. f

2. The developed film is washedgfor a short time to remove substantiallyall of the developer. 3. The washed film is then subjected to a combinedbleaching and mordanting process. For this purpose potassiumferricyanide may be used at usual concentrations; the opaque metallicsilver is oxidized to a translucent silver salt (silver ferro-cyanide),which serves to mordant the red-yellow dye of the bottom emulsion.

4. The film may then be immersed in a solution of basic blue dye such asmethylene blue which will mordant to the image in the outer emulsion b,but which will not affect the image in the inner emulsion.

5. The film is then given a short water wash to remove substantially allof the bleaching solution.

'6. The film is then treated with a fixing solution, such as sodiumthiosulphate, or any other well known clearing agent.

'7. The film is then washed in water to remove excess fixing solutionand excess blue dye.

8. The film is then washed in alcohol or other solvents, to wash awaythe unmordanted yellow to red dye in the inner emulsion.

9. The film is then dried.

In Fig. 3 the band or bands designated by the letter A show respectivelythe top emulsion 15 and the bottom emulsion c after development butbefore bleaching, and before the coloring of the top layer b. It is hereseen that on the top emulsion b, the black oblong is clear, because overthis area the emulsion was not affected and all of the silver salts canbe washed away.

The white oblong is registered as black on top emulsion b since this topemulsion is sensitive to white and therefore the metallic silver wasstrongly deposited. The blue oblong also affected the top .emulsion b,but with reverse values, the left half of this oblong being light grayand the right half a dark gray.

The green oblong similarly affects the top emulsion b.

The top emulsion b being insensitive toyellow 'and red, these twooblongs of the object produce clear areas in this top emulsion b.

Now let us consider the lower emulsion c of the same series A. The blackoblong of the object fails to register as the lower emulsion c isinsensitive to black; therefore the corresponding oblong on emulsion cis clear.

The white oblong of the object registers as a darkv red because itstrongly affects the lower emulsion.

Since the bottom emulsion c is not sensitive to blue, the-blue oblong ofthe object does not affect the lower emulsion c, and therefore itremains clear.

The green oblong of the object weakly aflects the emulsion c andtherefore it shows respectively as a light and dark yellow.

The same is true of the yellow oblong.

The red oblong of the object strongly ail'ects the lower emulsion c, andis shown in reversed the white oblong of the object registers as a blueoblong on the top emulsion b. The two gray oblongs corresponding to theblue and green of the object have now been colored light blue on theleft half and dark blue at the right half.

The finished negative N, is merely a superposition of two transparenciesb and 0. Black is shown as clear or white by transmitted white light.The white oblong ofthe object is reproduced in the negative as black dueto the superposition of the dark blue and the dark red.

The blue oblong of the object is represented as blue on the finishednegative, but with reversed value, and dark blue is shown as light andthe light blue is shown as dark.

The green oblong of the object is also shown as green in the negativebut with reversed values. The green tint is obtained by thesuperposition of the blue and yellow oblongs of the series B.

The yellow and red oblongs of the object are correspondingly reversed inthe negative, and are contributed solely by the lower emulsion c.

From this finished colored negative a contact print is made, using apositive film equal or similar in construction to that of the negativefilm, and with the following characteristics.

Upon a standard transparent base a light sensitive silver emulsion iscoated, exactly or similarly dyed as the bottom emulsion of thenegative.

An orthochromatic emulsion with a sensitivity similar to theorthochromatic emulsion in the negative is then coated on top of it.

A contact print is now made from the finished negative.

The processing method of the positive is exactly the same or similar asthat above described V for the negative, as an example of the practicalapplication of this invention.

The succemive steps are shown in Fig. 4.

It must be noted that all actinic records made for the blue sensitiveemulsion are colored blue and the records made for the yellow-redsensitive emulsion are colored yellow-red and that the double reversalof shade from black to white through blue, green, yellow and red resultsin a final print or photograph as shown in the bottom band of Fig. 4.

Thus the white oblong of the negative affects both the top and bottomemulsions b and c of the series D, of Fig. 4. This series represents thetop and bottom emulsions of the print after developing but beforebleaching and dyeing. The white oblong ofthe negative is printed blackon the top emulsion b and is printed red on the emulsion c. The blackoblong of the negative does not affect either emulsion b or c andtherefore the corresponding oblongs of b or c are clear.

The blue and green oblongs of the negative are shown as gray on the topemulsion of the print. On the bottom emulsion c of the print the bluedoes not register. The green registers as yellow with values reversed.

The yellow and red oblongs of the negative do not affect the topemulsion b and therefore the dyeing. Here the black oblong of the topemulsion B becomes blue and the corresponding gray oblongs on the topemulsion b become blue. The lower emulsion c has not altered in colorvalues.

Due to the superposition of the two emulsions b' and c the final printis a transparency having .the color characteristics as shown in thebottom band of Fig. 4. The white oblong of the negative is printed asblack. The black oblong of the negative is printed as white; The blueand green oblongs of the negative, are respectively shown as blue andgreen transparencies in the print with light values reversed. The greenoblong of the print is due to the combination of the blue and yellowtransparencies in theseries E.

The yellow and red oblongs of the negatives are contributed solely bythe lower emulsion c and are therefore the same as in the .series 1E.These are the same as the oblongs of the negative but with reversedcolor values.

Comparing the print of Fig. 4, with :the object of Fig. 3, it is seenthat the object has been faith- 1 for the two emulsions of negative andpositive films can be selected with the appropriate change of dye ortone values and processing details without departing from the principalcharacteristics of this invention.

It thus apparent that by providing a series of contacting emulsions,separately, and selectively sensitive to difierent portions of thespectrum, I-can produce a final result that is faithful without anydanger of misalinement between the varicolored layers, without thenecessity of using during the processing of these emulsions anyadditional colors or coloring agents, and without the necessity of usingany special coloring or printing machines-as are now necessary incommercially prevalent color processes, and with the use of standardcameras and projectors only. No filters need be used, although .undersome circumstances it may be advisable to accentuate or delete somecolor values, These advantageous results are due to the ability of thesensitive medium to do two things: first, to-be selectively tially so'as to subdue some of the color values.

I claim:

1. A method of producing photographic images in color on a film having aplurality of different light sensitive emulsions thereon one of saidemulsions being predyed the color to which it is predominantly lightsensitive which incldes: exposing said film to actinic light; developingthe respective latent images thereby obtained; mordanting the color inthe image carried by the predyed emulsion; selectively coloring anotherof said images the color to which the emulsion bearing said image waspredominantly light sensitive;

and removing the dye from the unexposed por-' tions of said predyedemulsion.

2,. The method of producing photographic images in color on a film.havinga plurality of diner-- ent light sensitive layers thereon, oneofsaid layers being predyed the color to which it is predominately lightsensitive, which includes: exposing said light sensitive layers toactinic light; developing the respective latent images thereby obtained;mordanting said images; selectively coloring the image in the undyedlayer; and removing the dye from the unexposed portions of said predyedlayer.

3. The method of producing photographic im-. ages in color on a filmhaving a plurality of different light sensitive layers thereon one ofsaid layers being predyed the color to which it is predomisaid lightsensitive layers to actinic light; devel- .30. nately light sensitive,which includes: exposing oping the respective latent images therebyobtained; mordantingsaid images; dyeing the image in the undyed layerblue; fixing said images and removing the color from the unexposedportions of said predyed layer.

4. The method of producing photographic images in color on a film havinga plurality of difierent light sensitive layers thereon, one of saidlayers being predyed the color to which it is predominately lightsensitive which includes: exposing said light sensitive layer to actiniclight; developing the respectivelatent images thereby obtained;mordanting the image in the predyed layer; dyeing the other image with abasic dye the color to which said layer was predominately lightsensitive; and washing said film in a spirit solution to remove theexcess dye in the predyed layer.

5. The method of producing photographic images in color on a film havinga plurality of difierent light sensitive emulsions thereon, one of saidemulsions being predyed the color to'which it is predominantly lightsensitive which includes: exposing said film toactinic light;developingthe respective latent images thereby obtained; selectivelycoloring the image in the emulsion which is not predyed the color towhich the emulsion bearing said image was predominately light sensitive;washing said film; and drying said film.

.LUDWIG M. DIETERICH.

